Process for preparing detergent compositions



De- 4, 1952 R. H. CHAFFEE ETAL 3,066,354

PROCESS FOR PREPARING DETERGENT COMPOSITIONS Filed July 25, 1960 ATTORNY.

Robert H. Chaifee, Cincinnati,

Patented Dec. 4, 1962 PROCESS FOR PREPARING DETERGENT COMPOSITIONS Ohio, Richard P. Laskey, Melbourne, Ky., and Oscar T. Quimby, Cincinnati, and Richard S. Bowles, Wyoming, Ohio, assignors to The Procter & Gamble Company, Cincinnati, Ollio, a corporation of Ohio Filed July 25, 1960, Ser. No. 45,197 Claims. (Cl. 18-47.5)

This invention relates to a tergent bars.

More particularly this invention relates to a process for preparing detergent bars involving the extrusion of a continuous shape-stable strip of the detergent.

The preparation of detergent bars in a more or less continuous manner by agitating a partiaUy solidified detergent mass within a critical temperature range and then extruding the partially solidified mass is well known. Such a process, as applied to soap, is described in Mills, U.S. Letters Patent No. 2,295,594. The Mills process applies the principle that above room temperature, at which temperatures soap masses of the type contemplated by Mills are in a solid state, certain temperatureranges exist in which those masses while in a soft pasty condition can be extruded in a shape-stable continuous strip, i.e., the extruded strip retains its cross-sectional shape and dimensions substantially unchanged until it has cooled to a substantially solid condition. The Mills process is effectively carried out by continuously introducing molten soap, along with any additives that may be desired, into one end of a scraped-wall heat exchanging and agitating device of the character disclosed, for example, in the patent to Vogt, No. 1,783,864, granted December 2, 1930, and its reissue, No. 21,406, granted March 19, 1940, and which is also illustrated in the aforesaid Mills patent. In the apparatus disclosed the soap is successively chilled while being subjected to intense agitation, is passed through a mixing chamber and extruded from the discharge end of the device through an orifice in a warm and pasty but shape-retaining condition as a continuous strip. This continuous strip is cut into segments which may be the size of individual bars, the segments are appropriately cooled and aged and are then formed into individual shaped tablets suitable for personal use.

The aforedescribed process is readily adaptable to the preparation of bars of many non-soap detergent formulations and formulations which include both soap and non-soap detergents in admixture-and this is true whether the ultimate detergent bars are to be non-aerated, aerated, or of the oating type.

In the preparation of detergent bars comprising watersoluble alkali metal soaps and an anionic organic synthetic detergent in admixture, and where the anionic synthetic detergent is an alkyl glyceryl ether sulfonate,l it was observed that the finished product prepared in accordance with the foregoing process of Mills exhibited a tendency toward mottling, that is, the finished detergent bars contained alternate opaque and translucent areas of detergent. Such mottling is readily visible to the human eye and may be likened to the mottling effect encountered in some types of marble. It adversely alfects the appearance of the bar product and its appeal to the customer, conveying, as it does, the impression of undesirable heterogeneity in the product rather than the desirable uniformity of appearance identified with product homogeneity.

It was further found that the mottling was also encountered at a sub-liminal visual level. This was readily evident from the examination of cross-sections of the detergent bar product under the microscope. Although such process for preparing deimottling does not adversely aiect the external visual appearance of the bar it is generally undesirable because of the attendant adverse effects upon the characteristics of the bar which contribute to diiiiculties in processing and ultimately upon the performance of the bar durrng use.

It is an object of this invention to provide detergent bars comprising in combination an alkyl glyceryl ether sulfonate detergent and a water-soluble alkali metal soap free from mottling.

It is a further object of this invention to provide a process whereby detergent bars free from mottling can be produced.

The FIGURE is a diagrammatic showing of a preferred form of apparatus for use in the practice of the process of this invention.

ln normal soap-making procedures, and this applies also in the case where a product is to comprise an admixture of soap and non-soapjsynthetic detergents, the detergent material, and any additives which it may be desired to use in the specific formulation, are usually mixed in a crutcher. This crutching operation is a normal and essential part of any soapor detergent-making process wherein it is desired to incorporate a num-ber of similar or dissimilar materials in the iinished product. It

is this type of mixing, utilizing a crutcher, and any mixing which is encountered in and is incidental to any subsequent pumping operations in the well-recognized soapmaking procedures in the art, that is referred to hereinafter and in the claims as the mixing encountered in normal soap-making procedures.

In such early processes, Where the detergent material and the desired additives were admixed in a crutcher and then merely poured into frames for cooling and solidification, and were subsequently cut into the appropriate bar sizes, the degree of mixing essential to the avoidance of mottling of bars comprising in combination an alkyl glyceryl ether sulfonate detergent and an alkali metal soap was never attained. Even in the process of Mills (see above), where additional mixing was accomplished incidental to the use of pumps and by passing the flowing detergent material through the particular cooling and agitating device described by that patentee, mixing of the detergent materials contemplated herein sutiicient to avoid the mottling problem could not be obtained. It

v is also to be appreciated, therefore, that the reference to the mixing encountered in normal soap-making procedures embraces the mixing which is accomplished in the Mills process.

It has now been found that detergent bars comprising in combination from about 15 to about 25% of an alkyl glyceryl ether sulfonate detergent and from about 60% to about 40% of a water-soluble alkali metal soap, in the form of neat soap, can be processed into finished bar products which are characterized by freedom from mottling. This objective can be essentially accomplished by subjecting the admixture of detergent materials (along with other additives if desired and which are common ingredients in detergent bars) to high-shear mixing such as is obtained by passing the material through a colloid mill or through a homogenizer. For example, a homogenizer of the Manton-Gaulin type (see Chemical Engineers Handbook, 3rd edition, John H. Perry, p. 1167 et seq.), wherein the detergent material to be processed is flowing at a rate of about 4500 pounds per hour and where the pressure drop across the homogenizing valve is in the range from about 500 to about 1500 p.s.i.g., has been found eminently suitable for the purposes of this invention. Other precautions, in conjunction with the aforementioned high-shear mixing, should also be observed, as will be evident hereinafter, if all mottling of the detergent bar is to be avoided.

desees/s The mottled appearance of the detergent bars contemplated herein is effected by two major factors. The first of these is an actual lack of homogeneity in the constituents in the make-up of the bar. As a result of this lack of homogenity among the constituents there is a tendency for the separate detergent ingredients, namely, alkali metal soap and alkyl glyceryl ether sulfonate, each to maintain its own identity in the finished product, a situation which can be considered akin to an emulsion of one of the detergent materials in the other. in addition, it has been observed that the tendency of the detergent bars of the compositions described herein to mottle is greatly enhanced if during the period subse uenttto' formation of the bars, when the temperature of such bars is usually reduced to about 100 F. or lower prior to the normal stamping and wrapping operations, the temperature of the bars is allowed to remain in the range of from about 110 to about 120 F. for periods of time in excess of about one hour. It is theorized that while the temperature of the bars is within this temperature range there is a tendency for the alkali metal soap to preferentially crystallize from the admixture of materials constituting the detergent bar. Moreover, and since within this range the critical temperature at which the alkyl glyceryl ether sulfonate begins to crystallize is encountered, `areferential crystallization of that constituent also takes place. Since, near the critical temperature the alkyl glyceryl ether sulfonate is at its highest concentration in the areas of the molten mass adjacent the already crystallized portion of the alkyl glyceryl ether sulfonate, these crystals tend to grow in size and this growth then tends to promote the separation of the alkyl glyceryl other sulfonate from the detergent mass in progressively larger and larger masses. In any event, it has been found that the longer the detergent bar is maintained in the aforesaid temperature range the greater the heterogeneity of the bar becomes, as evidenced by the larger and larger masses of the alkyl glyceryl ether sulfonate in the detergent bar product until finally, the heterogeneous character of the bar becomes visually apparent as it assumes a mottled appearance.

Although in the foregoing discussion the precautions as to temperature have been expressed in terms of detergent bars, such precaution must be observed with the detergent mass, after it has been reduced to substantial homogeneity by high-shear mixing, through any subsequent processing steps in the reduction of the said mass to finished detergent bars regardless of the processing methods employed.

The tendency toward mottling of the soap-alkyl glyceryl ether sulfonate mixture contemplated herein is believed to contribute essentially to diiculties encountered in preparing an aerated detergent bar comprising such detergent mixture. For example, such mottling has a pronounced eect upon the ability of the detergent mass to retain air and, therefore, also contributes to diiculties in controlling the density of the finished bar product-a factor which is rather critical when a floating bar is the desired end product. ln addition, and this would apply whether an aerated, floating, or non-aerated nal bar product is desired, the development of heterogeneity in the bar structure tends to weaken that structure and the bar, therefore, becomes very susceptible to breakage in use.

The alkyl glyceryl ether sulfonate component (i.e., the water-soluble salts of alkyl glyceryl ether sulfonic acid) in the detergent bars with which this invention is concerned contains from about l to about 18 carbon atoms in the alkyl group. These sulfonates can be made by first reacting fatty alcohols with epichlorohydrin and then reacting the alkyl chloroglyceryl ethers so formed with sodium or potassium suliites. The preferred source of the fatty alcohols which are used in the foregoing reaction is coconut oil and, in such products as are contemplated herein, the so-c-alled middle cut coconut alcohols are particularly advantageous. These middle cut coconut alcohols are derived from the coconut oil fraction having the following approximate composition:

Percent 10 carbon atoms 2 l2 carbon atoms 66 14 carbon atoms 23 16 carbon atoms 9 it being understood that in this fraction small amounts of material having less than 10 carbon atoms and more than 16 carbon atoms in the molecule are present.

Alkyl glyceryl ether sulfonates made in accordance with the process disclosed in the co-pending application of D. D. Whyte, Serial No. 627,131, tiled December l0, 1V56, now Patent No. 2,989,547, and which contain from about 10% to about 30% of the alkyl glyceryl ether sulfonate in the dimeric form, have been found particularly suitable in the detergent bar products contemplated herein.

The alkali metal soap components contemplated are any of the Water-soluble soaps normally used in toilet bar applications. The sodium soaps and, specifically, the sodium soaps made from different proportions of coconut oil and tallow are preferred. However, water-soluble soaps made from other fats or fatty acids can also be used'as will be evident to those skilled in the art. Also, and if desired, the aforementioned sodium soaps can be replaced in part by potassium soaps. However, because of the inherently greater solubility of the potassium soaps and because such soaps when substituted for sodium soaps characteristically tend to make a less lirm bar product, the amount of potassium soap which can be used is dependent upon the particular bar composition as well as upon the physical characteristics of the ultimate bar product which may be desired.

Although not limited thereto, this invention has been found to be particularly applicable and beneficial in the preparation of a tioating aerated detergent bar consisting essentially of: about 46% of a water-soluble soap, comprising in combination 50% of sodium coconut oil soap and 50% sodium tallow soap; about 23% of a sodium alkyl glyceryl ether sulfonate, wherein `the alkyl group is derived from the middle cut fatty alcohols obtained from coconut oil; about 2% glycerine; from about 1.0% to about 2.0% of sodium chloride; and about 23% moisture, other ingredients common to such bars as, for example, perfume, silicate, preservatives, being present in minor amounts.

This material was treated as follows, reference being made to the FGURE which shows diagrammatically the various component parts of an apparatus which can be used in the process of this invention. The alkyl glyceryl ether sulfonate and soap, both in molten condition, and containing respectively about 39.5% and about 30% moisture, were supplied to crutcher 1, along with other normal detergent additives and mixed. From this crutcher, wherein the mixture of materials was maintained at a temperature in the range of from about F. to about F., the mixture was pumped by pump 2, through a homogenizing valve 3, where it was subjected to highshear mixing, also at a temperature within the above range, and while in a non-crystalline condition, and heater 4, and was sprayed through spray-nozzle 5 into liash chamber 6. The heater 4, wherein the detergent admixture was heated to from about 390 to about 415 F., may be supplied with high pressure steam or other suitable heating medium and may conform in structure to any known type of heat exchange device for raising the temperature of liquids. The ash chamber 6 was provided at its upper end with a vapor tube 7 for the escape of volatilized moisture through a condenser 8, cold water or other condensing medium being supplied to the latter to effect condensation of the discharging vapor.

Following the reduction of moisture content of the detergent mixture in the ash chamber 6 to from about 18% to about 25 and preferably to about 22.5%, by Weight of the said mixture, the flash dried mixture was conveyed by pump 9 to and .through a continuous crutcher 10, where air, perfume and other additives were incorporated into the detergent mixture, and to a cooling device indicated generally by `11. In the cooling device 11, which was of the type more fully described in the aforesaid Mills patent, the detergent mass was cooled and agitated and was tinally extruded in a continuous strip through outlet orice 12, at a temperature in the range from about 120 to about 160 =F., and preferably at about 140 to about 145 vF., onto a traveling conveyor belt `13. The continuous strip was then separated into individual bar lengths by the cutter indicated schematically at 14 or by other suitable means.

The individual bar lengths were then cooled under controlled conditions of temperature and humidity--the humidity being controlled at about 80% relative humidity to prevent the bars from drying during cooling and the temperature of the ambient cooling air being controlled at about 75 F. Under these conditions the temperature of the individual bar lengths remains in the temperature range of about 110 F. to about 120 F. for less than 15 minutes.

-In the foregoing description the high-shear mixing, which, `along with the restriction on the time during which the temperature of the extruded detergent bars may remain in the 1il0 to 120 F. temperature range, is the crux of this invention, is accomplished through the use of a homogenizing valve under the conditions indicated. However, and as indicated hereinbefore, the invention is not limited to the use of a homogenizing valve for accomplishing the high-shear mixing. Other apparatus, such as a colloid mill, can also be effectively used provided that the work input -to such a mill is suicient to achieve the desired ends.

Also, the foregoing description `and accompanying drawing are not to be construed as limiting of the point in the process of this invention where the high-shear mixing of the detergent material is to take place. Such mixing can be carried out on the detergent mixture while in a non-crystallized condition at any point in the process prior tothe time the detergent material enters the cooling] and agitating device depicted. In addition, the process described is not limited to a continuous operation, in which sense the process description above has been couched. It is also fully adaptable, if desired, .to a batch type operation.

The amount of high-shear mixing which is required to accomplish the objects of this invention and eliminate the mottling in =a given soap-alkyl glyceryl ether sulfonate mixture dees accurate measurement and the adequacy of the mixing can only be determined from an examination of the finished detergent bar product. (This, of course, presupposes that the precautions as to the time during which the bars contemplated herein are at a temperature in the range from about 110 to about 120 F. have been observed.) When a Manton-Gaulin homogenizing valve is used as the high-shear mixing device, a pressure drop across this valve of from about 500 to about 1500 p.s.i.g., at a ow rate of the detergent mass of about 4500 pounds per hour, has been found to accomplish the desired ends.

In the preparation of aerated detergent products such as have been described hereinbefore, additional diiculties can be encountered in obtaining a nished product having a good surface and adequate and uniform air dispersal throughout the detergent mass. In a co-pending application of Robert H. Chaffee and Richard S. Bowles, two of the inventors in the present application, Serial No. 45,198, led July 25, 1960, apparatus and methods are disclosed which facilitate the overcoming of such diculties through the provision of means whereby the detergent mass, during cooling and agitation in the 6 extruding apparatus, is subjected to a back-pressure suflicient to maintain ra major portion of the incorporated compatible gas in solution in said mass. Such apparatus and methods as described therein are eminently suitable for use in conjunction with the process of this invention.

Although the foregoing description has `been directed primarily toward the production of aerated detergent bars, it is to be understood that the process of this invention is equally beneficial when non-aerated detergent bars are to be made. For example, a sodium alkyl glyceryl ether sulfonate and sodium soap while in molten ocndition can be admixed in a crutcher, along with any additives desired, care being taken not to incorporate air in the mass during the crutching operation, subjected to the high-shear mixing of the process of this invention by passage through a homogenizer or colloid mill vand then merely poured into a frame or some shape-imparting means for cooling and solidiiication. With non-aerated detergent bars so produced the precautions with regard to residence time of the cooling mass in the temperature range from about to about 120 F. hereinbefore advanced must be observed.

Having thus described the invention, what is claimed is:

1. In a process for preparing detergent bars from a heated iiowable detergent mass comprising, in combination, from about 15 to about 25% of an a kyl glyceryl ether sulfonate detergent and from about 60% to 40% of a water-soluble alkali metal soap, which combination, when subjected to mixing by soap making procedures comprising crutching, cooling, agitating and pumping is, characterized by a tendency to form detergent bars having a mottled appearance, the steps which comprise (l) subjecting the heated combination, while in a noncrystalline condition to high shear mixing equivalent to the degree of mixing obtained by a pressure d-rop across a homogenizing valve in the range from about 500 to about 1500 p.s.i.g., and suicient to reduce the combination to substantial homogeniety, and (2) after mixing, agitating, and reducing said homogeneous mixture to nished deter-- gent bars at temperature above about F., cooling said bars through the temperature range of from about 120 F. to about 110 F. in a period of time not more than about 1 hour such that preferential crystallization of the detergent components from the mixture is prevented, whereby any tendency to form detergent bars having a mottled appearance is essentially eliminated.

2. The process of claim 1 wherein the alkali metal soap and alkyl glyceryl ether sulfonate are present in the noncrystalline combination in the ratio of about 2:1.

3. The process of claim 1 wherein the alkali metal soap in the non-crystalline combina-tion comprises 50% sodium coconut oil soap and 50% sodium tallow soap.

4. The process of claim 1 wherein the high-shear mixing is accomplished by passing the non-crystalline alkali metal soap-alkyl glyceryl ether sulfonate combination through a homogenizing valve, the pressure drop across said valve being in the range from about 500 to about 1500 p.s.i.g.

5. A process for preparing aerated `detergent bars from a owable detergent mass comprising in combination from about 15% to about 25% of an alkyl glyceryl ether sulfonate detergent and from about 60% to about 40% of a water-soluble alkali metal soap, the said combination, when admixed by soap-making procedures comprising crutching, cooling, agitating, and pumping, being characterized by a tendency to form detergent bars having a mottled appearance, which comprises (l) admixing the said alkyl glyceryl ether .sulfonate and alkali metal soap, (2) subjecting the admixture, while in non-crystalilne condition, to high-shear mixing equivalent to that degree of mixing obtained by a pressure drop across a homogenizing valve in the range of about 500 to 1500 p.s.i.g. and suiiicient to reduce the admixture to substantial homogeneity, (3) reducing the moisture content of the resulting homogeneous mixture, (4) incorporating in and uniform- 1y distributing throughout the said homogeneous mixture a compatible gas in an amount sufficient to impart to the finished detergent bars a density less than that of water, (5) cooling the resulting aerated mass, (6) agitating the said mass during cooling and immediately subsequent thereto, the said cooling and agitating being carried out at a pressure sufficient to maintain a major portion of the compatible gas in solution in the said mass, (6) extruding the cooled and agitated aerated mass through an orice in the form of a continuous shape-retaining strip at a temperature in the range from about 120 to about 160 F., (8) cutting the said continuous strip into individual detergent bar lengths and (9), during subsequent cooling 0f the said individual bar lengths to a temperature below about F., cooling the temperature of the individual bar lengths through the temperature range from about F. to about 110 F. `for a period of time not more than about one hour such that preferential crystallization of the detergent components in the detergent mass is prevented, whereby any tendency of the alkali metal soapalkyl glyceryl ether sulfonate mixture to form mottled detergent bars is essentially eliminated.

References Cited in the tile of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR PREPARING DETERGENT BARS FROM A HEATED FLOWABLE DETERGENT MASS COMPRISING, IN COMBINATION, FROM ABOUT 15% TO ABOUT 25% OF AN ALKYL GLYCERYL ETHER SULFONATE DETERGENT AND FROM ABOUT 60% TO 40% OF A WATER-SOLUBLE ALKALI METAL SOAP, WHICH COMBINATION, WHEN SUBJECTED TO MIXING BY SOAP MAKING PROCEDURES COMPRISING CRUTCHING, COOLING, AGITATING AND PUMPING IS, CHARACTERIZED BY A TENDENCY TO FORM DETERGENT BARS HAVING A MOTTLED APPEARANCE, THE STEPS WHICH COMPRISE (1) SUBJECTING THE HEATED COMBINATION, WHILE IN A NONCRYSTALLINE CONDITION TO HIGH SHEAR MIXING EQUIVALENT TO THE DEGREE OF MIXING OBTAINED BY A PRESSURE DROP ACROSS A HOMOGENIZING VALVE IN THE RANGE FROM ABOUT 500 TO ABOUT 1500 P.S.I.G., AND SUFFICIENT TO REDUCE THE COMBINATION TO SUBSTANTIAL HOMOGENIETY, AND (2) AFTER MIXING, AGITATING, AND REDUCING SAID HOMOGENEOUS MIXTURE TO FINISHED DETERGENT BARS AT TEMPERATURE ABOVE ABOUT 120*F., COOLING SAID BARS THROUGH THE TEMPERATURE RANGE OF FROM ABOUT 120* F. TO ABOUT 110*F. IN A PERIOD OF TIME NOT MORE THAN ABOUT 1 HOUR SUCH THAT PREFERENTIAL CRYSTALLIZATION OF THE DETERGENT COMPONENTS FROM THE MIXTURE IS PREVENTED, WHEREBY ANY TENDENCY TO FORM DETERGENT BARS HAVING A MOTTLED APPEARANCE IS ESSENTIALLY ELIMINATED. 